Telefunken RT200 User Information page 7

Available Documents
Manual
Service Manual/Circuit Diagram
Goodies
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Replacing The Broken Microprocessor in a Telefunken RT200
Introduction
NOTE: This is a project for people who are absolutely crazy, like me. It took me altogether more than two
months of work to do this project, not counting the hassle to find appropriate information (and realizing
that I had to find out things myself). This report mostly has documentational purposes and there is probably
noone who has an RT200 with the same problem and can use this text as a 1:1 guide. To do something like
this, you need to have experience in reverse engineering devices, understanding both analog and digital
electronics, building hardware, and programming embedded controllers. If you try something similar along
the lines of this project, you are absolutely on your own and I might not be able to help you out. Especially,
you are yourself responsible for anything you break. So for the moment, lean back, read, enjoy, and see if
you can reuse some aspects for your projects.
The root of this project is one of my collecting passions, Telefunken Hifi components built in the late
70s/early 80s. The RT200 is an FM/AM Tuner with a built-in timer clock, i.e. you may use it to switch
other devices on and off at preprogrammed times. Typically, those were the cassette deck and/or amplifier,
either to wake yourself in the morning with a sound quality better than any alarm radio clock or make
unattended recordings of radio programs.
I bought this RT200 for a few bucks at a flea market. Normally, there are few things in a synthesizer-based
digital tuner that can break: no movable parts except for the buttons, no lamps to burn out, just a NiCd
accumulator that may start to leak after a couple of years of operation. This RT200 however was perfectly
dead: plug it in and you won't get any reaction to key presses, just a few cryptic symbols on the display.
Checking the parts that are usually broken in such a case (power supply, clock generator) revealed nothing,
so it was clear that the central microprocessor chip had passed away. A truly uncommon event, so I guess
this happened due to incompetent repair attempts by the previous owner.
front plate, cpl.
side part f. front plate
frame f. tuning knob
button frame
buttons guiding, 8 fold
indicator window
display frame
push button holder
push button spring
housing, upper part
housing, rear panel
foot
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